U.S. Pat. No. 3,390,559 issued to O. M. Steutzer on July 2, 1968 illustrates a lock effectuated by a round piezoelectric clamp having a circular cross section for the internal gripping of a lock cylinder. This gripping device must have a good match with the interior of the tube in order to exert a substantial frictional force between the outside of the piezo cylinder and the interior surface of the tube.
U.S. Pat. No. 3,952,215 issued to Y. Sakitani on Apr. 20, 1976 discloses a device for adjusting a holder for microscope specimens in which stepwise adjustment is provided by sequential activation of a set of piezoelectric pieces. The adjusting device is held in position by electrostatic force between a dielectric plate and a base plate.